I'm moving along with some development of the next version of Bookcase, 0.7. I added a new field type, Table, intended primarily for things like a list of the songs on an album. The Paragraph type could be used, but I think it's cleaner to use a table. And it does look ok.
I had been planning to allow a file to have multiple collections, and I got so far as implementing it, along with a nice icon tool bar and everything, but I ended up deciding that I wanted my UI to remain simple. So, only one collection per file. But I've got skeletons for music and video collections, and thoughts about coins, stamps, trading cards, etc.
Thus, the Table type...I need it so I can have a list of songs on an album, or chapters on a DVD.
I also changed the Year type to Number, which is more generic, and lets me do numerical sorting more easily in the column view.